Magnetic read-write heads are used in the recording and retrieval of digital information from magnetic discs, magnetic tape, or other information storage devices. The magnetic heads typically include one or more thin layers of magnetic material that is oriented to generate a magnetic field that alters the recording media, or to sense a magnetic field on the recording media without interference. The thin layer of magnetic material is typically deposited on a substrate that is used to prepare the magnetic recording head.
FIG. 1 (prior art) illustrates a typical magnetoresistive head 5 that reads information from magnetic medium 6. The magnetoresistive head 5 includes a soft magnetic layer 7 (e.g., 80% nickel, 20% iron) that functions as the magnetoresistive sense layer, and a hard magnetic layer 8 (e.g., 75% nickel, 20% iron, 5% chromium). The magnetic layers are deposited on a non-magnetic substrate 4 such as aluminum oxide or an alloy of aluminum/titanium/carbon. The soft magnetic layer 7, and the hard magnetic layer 8, are separated by a spacer layer 9 (e.g., tantalum). The magnetic layers are typically manufactured by sputtering a target comprising the metal alloy to deposit particles of the metal alloy onto a substrate positioned within a magnetic field. The magnetic field orients the depositing particles and magnetizes the deposited film. Performance of the magnetic heads is enhanced by depositing the thin film within a substantially parallel magnetic field, as described in U.S. Pat. No. 5,589,039. Sputtering of the target can occur within a magnetic field as known in the art. However, uniform magnetic fields having a high degree of parallelism at a substrate are difficult to maintain within a sputtering chamber because of interference between the magnetic field at the substrate and a plasma generated within a magnetic field at the target.
U.S. Pat. No. 5,660,744 describes a circular magnet array that is located outside an etch chamber and includes a plurality of magnets that form a parallel magnetic field. In the '744 patent, two external circular magnet arrays are used in conjunction with an electric field to enhance an etching process. The circular magnet arrays generate parallel magnetic fields that are out of phase and are not positioned to form a parallel magnetic field at a surface of a substrate.
Elimination of interference between a plasma generated adjacent a metal alloy target and a parallel magnetic field at the surface of a substrate would substantially improve the manufacture of magnetic films such as used in magnetoresistive heads. Therefore, there is a need for a sputtering chamber that provides a parallel magnetic field at the substrate surface without substantial interference from charged particles.